Shane Tamura, the 27-year-old shooter who fatally shot himself, was a former standout high school football player who claimed he suffered from CTE, the brain disease that has been found to be common in football. Chronic Traumatic Encephalopathy is a degenerative brain disease that occurs with repeated head injuries.

Investigators found the note in the wallet of 27-year-old shooter Shane Tamura who police said opened fire inside of 345 Park Avenue.

Shane Devon Tamura, who killed at least four people in N.Y.C. before turning the gun on himself, claimed in his suicide note that he had brain disease CTE